This project consists of four subprojects. The objective of the first is to determine the effect of both quantity (65 Cal/kg.d vs. 130 Cal/kg.d) and quality (0.5 gm/kg.d vs. 3 gm/kg.d as fat with the remainder as glucose) of parenteral caloric intake on nitrogen retention and the serum hormone-substrate profile. The second subproject concerns the metabolism of intravenously-administered fat emulsions. The objective of the third subproject is to define the parenteral requirement for all amino acids. In this context, the requirement for each amino acid is defined as that intake resulting in a plasma concentration within the 95% confidence limits of the 2-hour post-prandial plasma concentration observed in normal infants. The fourth subproject is designed to provide information concerning bile salt metabolism during parenteral nutrition, specifically to define the changes occurring as a result of the lack of stimulation of the enterohepatic circulation. Data collected in all subprojects will also be helpful in defining the clinical efficacy of parenteral nutrition and are likely to suggest ways for improving the current practice of parenteral nutrition.